Holley Carb ?

[kman67rsss]

Looking for some info on converting a holley 4160 to a 4150. the old man has a 4160 on his 350 crate in the 34, and hasent read too many good things about it. im looking into it for him. whats involved, whats the advantages? thanks for the help

[Zee]

The only advantage of significance is the replacable rear main jets. Holley sells a kit that includes a rear metering block, longer transfer tube and longer screws. Every 4160 I have ever had was immediately converted to a 4150 so I can't even tell you how the metering plate works. You need the adjustibility if you are into performance.

[cad]

You cannot actually convert a 4160 to a 4150. It is a misnomer of sorts.
You can only add the metering block for the secondaries.
Inserting a screw in the secondary throttle blade mechanism is not a 4150, either.
http://www.holley.com/TechService/Library.asp

[Zee]

Outside of list numbers, what is the difference between a 4150 and 4160 then?

[cad]

Pg6 of this document, available at the Holley link listed earlier, http://www.holley.com/data/TechServi...ech%20Info.pdf covers a couple basic differences.

[Zee]

Okay, you lost me. Page 6 refers to the seconday opening system, not fuel metering. I don't believe the original posting was referring to converting vacuum secondary carb to mechanical secondaries. The 4150 comes in both vacuum and mechanical secondaries. My understanding is the primary distinction is the secondary metering block which Holley offers in their 4160-4150 conversion kit PN 34-6. I don't think Holley would offer a kit to do this conversion if it were not possible: http://www.holley.com/products.asp?product=34-6

[cad]

That kit will not convert a 4160 to a 4150.
A 4150 is mechanically-actuated secondary fuel delivery.
The kit just replaces the metering plate in the secondary, making tuning more flexible as the metering plates only come in a handful of sizes.

[Zee]

The 4150 comes in both mechanical and vacuum secondaries. The best example would be the 3310 which comes in both a 4150 and a 4160 version. The 3310-1 has a rear metering block making it a 4150 while the 3310-3 has a metering plate which would require the previously mentioned conversion kit. Here's a link to Motec's site which has the list numbers as well as model numbers. Scroll down to the 3310 and you will see it is listed as both a 4150 and a 4160. The difference has nothing to do with seconday actuation. Although all square bore mechanical secondary Holleys are 4150's (outside of the 4010 series), not all 4150's have mechanical seondaries.

http://www.mortec.com/carbs.htm

[gmachinz]

Anymore it seems, the "3310" is used to generically describe a 750cfm Vacuum secondary Holley carb. The biggest (and really only) difference between the two families of carbs is the primary idle circuits. One is more race oriented while the other is more geared for the emmision laden vehicles, which refers to where the leaning comes from-either idle port/transfer passage or an auxillary bleed hole at the base of the venturi. For this reason, you can't really convert from a 4150 to a 4160 and vice versa but you can use the 34-6 kit to allow you to do change rear jets. A metering plate flows about like having a pair of #74 jets in the rear. Not really a lot if the motor is modified extensively. By having a rear block though you can also tailor secondary fuel delivery by modifying the idle feed restrictions but if you don't have a pretty good understanding (or even a need for...) doing so then you shouldn't tackle that, anyway. I like changing rear jets so I'd do that no matter what. Other issues to sort out are what size accel. pump? Accel. pump cam? Jet size? Booster size? Squirt nozzle size? Secondary spring type-if equipped? You may need to dis-assemble the carb to figure out which version you have because an emmisions style carb won't work without major changes to the idle circuits to work well on a modified motor. -Jabin